An Ecuadorian judge on Wednesday opened a criminal trial against former president Rafael Correa and three others in connection with the attempted kidnapping of a former lawmaker.

However, judge Daniella Camacho suspended the beginning of the trial against Correa until he surrenders or is apprehended as he cannot be tried in absentia. The former head of state has resided in Belgium since 2017.

Correa, who was president from 2007 to 2017, is suspected of involvement with the attempted kidnapping of former lawmaker Fernando Balda in Bogota in 2012.

The preliminary hearing for the trial lasted more than three hours and was confidential; it was only attended by the parties' attorneys, prosecutor Ruth Palacios and Balda.

The judge's ruling came in response to a prosecutor's office request in September to summon Correa and three others to stand a criminal trial, after it found elements for a conviction.

The former head of Ecuadorian intelligence agency Senain, Pablo Romero, and police officers Raul Chicaiza and Diana Falcon are the other three defendants summoned to stand trial.

The agents entered a witness protection programme when they declared that Correa ordered the kidnapping.

Balda, who helped Correa's party co-draft the 2008 constitution but later turned against the president, had fled to Colombia to avoid being jailed on charges of insulting the government and endangering national security.

He was briefly kidnapped before being released by Colombian police.

His abductors went on trial in Colombia and reported the involvement of the Senain, which takes orders from the president. Correa allegedly wanted to take Balda back to Ecuador to jail him.

The ex-president, who denies the accusations, told Latin American television network Telesur moments before the ruling that the Balda case should be understood as "part of a regional strategy against the Left."

After the ruling, he took to Twitter to call the case a "farce."

"It's all political persecution, because they can't defeat the ballot box," Correa wrote.

Camacho had earlier ordered the preventive detention and arrest of Correa after he failed to obey orders to report to the tribunal in Quito every two weeks.